Goyal Brothers Prakashan solutions for अ न्यू अप्रोच टू आईसीएसई [अंग्रेजी] कक्षा १० chapter 6 - Sound [Latest edition]

What is an echo?

State two practical uses of the phenomenon of echo.

How do bats avoid obstacles in their way, when in flight?

Speed of sound in air is 330 ms⁻¹. A man standing at a distance of 165 m from a high wall, claps his hands.

1. Will the man hear a distinct echo?
2. Give a reason for your answer in (i).

A man standing between two cliffs fires a gun and hears an echo after every one second. The distance of the man from the nearest cliff is 170 m, calculate:

1. velocity of sound,
2. distance between two cliffs.

Explain, why an under water explosion recorded by sonar is about 4.5 times faster than heard through air.

A boy sets up a simple pendulum which makes four oscillations per second. The boy then stands in front of a high wall and blows a whistle. He hears an echo, after 6 oscillations of the pendulum. If the speed of sound in air is 330 ms⁻¹, what is the distance between the boy and the wall?

What is 'SONAR'?

State the principle on which SONAR is based.

An instrument is able to detect the reflected waves from an enemy aeroplane, after a time interval of 0.02 milliseconds. If the velocity of the waves is 3 × 10⁸ ms⁻¹, calculate the distance of the plane from the radar.

1. Name the wave used for echo depth sounding.
2. Give one reason why the waves mentioned in (a) is used for the above purpose.

A man standing 25 m away from a wall produces a sound and receives a reflected sound. It the speed of sound is 350 ms⁻¹, after what time he hears sound?

The practical application based on the reflection of sound is:

Which is not the condition for the formation of echoes?

For hearing an echo, the minimum distance between the source of sound and reflecting body should be:

To locate its prey in the darkness the owl or the bat emits:

AB is a sound wave striking a high wall at an angle of 20°.

The angle between the incident ray and the reflected ray is :

The persistance of audibility for a normal human ear is:

The repetition of sound after reflection from a distant object, after original sound from a given source dies, is called ______.

After the thunder of a cloud, hearing of series of echoes from different reflectors is called:

Sonar uses ultrasonic vibrations because, ultrasonic vibrations ______.

If the speed of ultrasound in water is 1600 ms⁻¹ and an impulse sent by the sonar is received by the observer in 3.6 s, then the depth of sea is:

The echoes are used in:

Echoes are not used by:

A person fires a gun in front of high-rise building 167 m away. If the velocity of sound is 339 ms⁻¹, the time for hearing echo, after the firing of gun is:

A person fires a gun in front of hillock situated at a distance of S from the person and hears the echo after 1.5 s. If the speed of sound is 310 ms⁻¹, the value of S is:

A boy explodes a cracker in front of a high-rise building 132.8 m away and hears an echo after 0.8 s. The speed of sound in air is:

An echo is heard by a radar in 0.08 s. If the velocity of radio waves is 3 × 10⁸ ms⁻¹, the enemy plane is at a distance of:

A man stands in between two high-rise buildings and explodes a cracker. He hears two successive echoes after 0.8 s and 1.6 s. The distance between two high-rise buildings is:

Assertion (A): Sound waves necessarily require a medium for their propagation.

Reason (R): The transfer of energy by the waves is through the vibrations of the medium particles about their mean positions.

Assertion (A): Longitudinal waves can travel only in solids and on the surface of liquids.

Reason (R): Transverse waves can travel in solid, liquid as well as in gas.

Assertion (A): If the reflector is at a distance less than 17 m, the reflected sound gets as an echo.

Reason (R): If there are repeated reflections at the reflected surface, the sound gets prolonged. This effect is known as reverberation.

The phenomenon of echo is based on the ______ of sound.

Radar is based on the reflection of ______ waves.

______ waves are used in sonar because they do not get scattered easily.

Sound travels about ______ time faster in water than in air.

In ultrasonography the mechanical waves employed are ______.

Match the statements in Column A with those in Column B.

A boy stands 83 m in front of a high wall and then blows a whistle. Calculate the time interval when hears an echo. Speed of sound is 332 ms⁻¹.

A person fires a gun in front of a building 167 m away. If the speed of sound is 334 ms⁻¹, calculate the time in which he hears an echo.

An echo is heard after 0.8 s, when a person fires a cracker, 132.8 m from a high building. Calculate the speed of sound.

The speed of sound is 310 ms⁻¹. A person fires a gun. An echo is heard after 1.5 s. Calculate the distance of the person from the cliff from which the echo is heard.

The radiowaves travel at a speed of 3 × 10⁸ ms⁻¹. If a radar can hear an echo from an enemy plane in 0.015 milliseconds, how far is the enemy plane from the radar?

An echo is heard by a radar in 0.08 s. If velocity of radio waves is 3 × 10⁸ ms⁻¹, how far is the enemy plane?

An enemy plane is at a distance of 300 km from a radar. In how much time the radar will be able to detect the plane? Take velocity of radio waves as 3 × 10⁸ ms⁻¹.

A man stands in between two parallel cliffs and fires a gun. He hears two successive echoes after 2 seconds and 4.5 seconds. What is the distance between the two cliffs? [Speed of sound = 332 ms⁻¹]

A man stands in between two high rise buildings and blows a whistle. He hears two successive echoes after 0.4 s and 1.6 s. Calculate the distance between the buildings. [Speed of sound = 332 ms⁻¹]

A man stands in between two parallel cliffs and explodes a cracker. He hears the first echo after 0.6 s and the second echo after 2.4 s. Calculate the distance between the cliffs. [Speed of sound is 336 ms⁻¹]

A man stands in between two cliffs X and Y, such that he is at a distance of 66 m from X. When he blows a whistle he hears the first echo after 0.4 s and the second echo after 1.2 s. Calculate : (a) speed of sound (b) distance of cliff Y from the man.

A man stands in between two cliffs, such that he is at a distance of 133.6 m from the nearer cliff. He fires a gun and hears the first echo after 0.8 s and the second echo after 1.8 s. Calculate : (a) speed of sound (b) distance between the two cliffs.

A person stands in between two parallel cliffs which are 99 m apart. He fires a gun and hears two successive echoes after 0.2 s and 0.4 s. Calculate : (a) the distance of the person from the nearer cliff (b) speed of sound.

A man stands in front of a cliff and fires a gun. He hears an echo after 4 seconds. On moving closer to the cliff by 41.25 m and again firing a gun, he hears an echo after 3.75 s. Calculate : (a) speed of sound and (b) distance of the man from the cliff to his initial position.

A person standing in front of a cliff fires a gun and hears its echo after 3 s. If the speed of sound in air is 336 ms⁻¹.

1. Calculate the distance of the person from the cliff.
2. After moving a certain distance from the cliff, he fires the gun again, and this time the echo is heard 1.5 s later than the first. Calculate the distance that the person moved.

A boy stands in from of a cliff on the other side of a river. He fires a gun and hears an echo after 6 seconds. The boy then moves backward by 170 m and again fires the gun. He hears an echo after 7 seconds. Calculate
(i) width of river,
(ii) speed of sound.

Define: Natural vibrations and support your answer by two examples.

Define: Forced vibrations and support your answer by two examples.

What is meant by resonance?

State two conditions under which resonance takes place.

Explain why does a wine glass starts rattling, when a note of some particular frequency is struck by a piano?

When a tuning fork (vibrating) is held close to ear, one hears a faint hum. The same [vibrating tuning fork] is held such that its stem is in contact with the table surface, then one hears a loud sound. Explain.

Explain Why are stringed musical instruments provided with large sound boxes?

Sometimes when a vehicle is driven at a particular speed, a rattling sound is heard. Explain briefly, why this happens and give the name of the phenomenon taking place.

Suggest one way by which the rattling sound can be stopped.

1. A person is tuning radio-set to a particular station. What the person is trying to do during tuning?
2. Name the phenomenon involved in tuning radio set.
3. Define the phenomenon named by you in (b).

State two ways in which resonance differs from forced vibrations.

Distinguish between the free (or natural) and forced vibrations.

Distinguish between natural and damped vibrations.

The following diagram shows the displacement – time graph of the vibrating body.

1. Name the kind of vibrations
2. Give one example of such vibrations.
3. Why is the amplitude of vibrations gradually decreasing?
4. What happens to the vibrations of the body after some time?

A bucket kept under a running tap is getting filled with water. A person sitting at a distance is able to get an idea when the bucket is about to be filled.
(i) What change takes place in the sound to give this idea?
(ii) What causes the change in the sound?

A vibrating tuning fork is placed over the mouth of a burette filled with water. The tap of the burette is opened and the water level gradually starts falling. It is found that the sound from the tuning fork becomes very loud for a particular length of the water column.

1. Name the phenomenon taking place when this happens.
2. Why does the sound become very loud for this length of the water column?

In the diagram below, A, B, C, D are four pendulums suspended from the same elastic string PQ. The lengths of A and C are equal to each other, while the length of pendulum B is smaller than that of D. Pendulum A is set into a mode of vibrations.

1. Name the type of vibrations taking place in pendulums B and D.
2. What is the state of pendulum C?
3. State the reason for the type of vibrations in pendulums B and C.

The above picture shows a mother pushing her daughter sitting on a swing. The swing is going through the positions A, B, C where A and C are extreme positions and B is the mean position.

1. Which is the right position i.e. at A, B or C, for the mother to give a constant periodic push to the swing every time in the forward direction to increase the amplitude of the swing?  (1)
2. Name the phenomenon involved in this.  (1)
3. Explain with this example how this phenomenon helps to increase the amplitude of the swing.  (2)

A string is stretched between two nails fixed in the opposite walls and plucked from middle. The vibrations produced by the string are:

Water from a tap is allowed to fall in a vessel with a thin neck. The pitch of sound produced by falling water ______ with the volume of water in the vessel.

The amplitude of forced vibrations is generally ______ than the amplitude of applied external force.

A tuning fork has a frequency of 212 Hz. It will produce resonance in a wooden board of frequency:

Which is not true for free vibrations?

Which are the characteristics of damped vibrations?

The vibrations which take place under the influence of an external force are called:

Which are characteristics of forced vibrations?

The phenomenon which takes place when the natural frequency of a given body is equal to the natural frequency of a vibrating body is called:

A burette is filled with water upto its neck and clamped vertically in an iron stand. The water is allowed to trickle drop by drop in a beaker and a vibrating tuning fork is held above the neck of the burette. It is observed that at some particular depth the loudness of sound of the tuning fork rises. The phenomenon which takes place is:

If the wavelength of a note increases, its:

The loudness of a note decreases if:

A wire of length 80 cm has a frequency of 256 Hz. If another wire of same material and same diameter has frequency of 1024 Hz, the length of wire is:

Assertion (A): All bodies on being disturbed start vibrating with a definite frequency, thereby producing vibrations.

Reason (R): The vibrations produced by a disturbance are called free vibrations.

Assertion (A): The free vibrations are simple harmonic vibrations under a restoring force in which amplitude and frequency are constant.

Reason (R): The vibrations of constant amplitude and frequency can occur only in vacuum.

Assertion (A): The amplitude of damped vibrations generally decreases with time and at the end vibration stops.

Reason (R): In each vibrations there is a progressive loss of energy.

Assertion (A): The frequency of free vibrations depends on the shape and size of object.

Reason (R): The frequency of free vibrations is a variable quantity.

The periodic vibrations of continuously decreasing ______ in the presence of resistive force are called damped vibrations.

The periodic vibrations of a body of constant amplitude in the absence of any ______ force are called free vibrations.

The vibrations which take place under the influence of an external periodic force are called ______ vibrations.

When the needle of a gramophone player moves in the grooves of a record, it produces ______ vibrations.

In case ______ vibrations, the amplitude of vibration is very large, compared to the amplitude of vibrations of external force.

Match the statements in Column A with those in Column B.

Define:

Musical Sound

Define the following term:

Noise

State three characteristics of noise.

Define the term "Pitch of musical sound".

How does the pitch of a musical note depend upon frequency?

How does the pitch of a musical note depend upon wavelength?

Are ‘pitch’ and ‘frequency’ of a musical note same? If not explain.

Which of the two ‘pitch’ or frequency of a musical note is subjective and why? Explain with an example.

Define the term “Loudness of musical sound or intensity of musical sound”.

Are “loudness of sound” and intensity of sound same? If not explain.

How does intensity of musical sound depend upon amplitude of sound wave?

How does intensity of musical sound depend upon distance of observer from the source of sound?

How does intensity of musical sound depend upon density of a medium in which sound travels?

Name two factors on which loudness of sound depends.

Name the unit in which loudness of sound is measured.

Define one decibel.

What is the normal range of loudness for humans?

What do you understand by the term quality of musical sound?

Is the quality of musical sound a subjective or objective characteristic of a musical note? Explain.

Why do the different musical instruments producing note of same frequency, same amplitude have different quality?

What adjustments will you make for tuning a stringed instrument, such as violin for it to emit a desired pitch?

In what respect does the wave pattern of a noise and a music differ? Draw diagram to explain your answer.

Why are wires of different thickness and different lengths provided on the same musical instrument?

Why can a person easily recognise the horn of his own car, no matter most of the cars use the factory made horn of same quality?

List two sources of noise in on roads.

List two sources of noise in homes.

List sources of noise pollution in your surroundings.

List two sources of noise in factories.

What is meant by noise pollution?

State any two harmful effects of noise pollution on human health.

State any four measures to control noise pollution.

Two waves of the same pitch have their amplitudes in the ratio 2 : 3.
(i) What will be the ratio of their loudness?
(ii) What will be the ratio of their frequencies?

Name the subjective property of sound related to its frequency.

Name the subjective property of light related to its wavelength.

Which characteristics of sound will change if there is a change in its amplitude.

Which characteristics of sound will change if there is a change in its waveform.

Name one factor which affects the frequency of sound emitted due to vibrations in an air column.

The adjacent diagram shows three different modes of vibrations P, Q and R of the same string. 

(i) Which vibration will produce a louder sound and why?
(ii) The sound of which string will have maximum shrillness?
(iii) State the ratio of wavelengths of P and R.

The amplitude of a sound wave is increased from 1 mm to 2 mm. The loudness of the sound will:

By decreasing the amplitude of a pure note its:

Two notes are produced from a flute and piano, such that they have same loudness and same pitch. The notes so produced differ in their:

The voice of women is shrill as compared to men because of the difference in their:

Two sound waves X and Y have the same amplitude and the same wave pattern but their frequencies are 60 Hz and 120 Hz respectively, then ______.

Assertion (A): Strings of different thicknesses are provided on a stringed instrument.

Reason (R): Notes of different frequencies can be obtained by producing vibrations in different strings having different thicknesses.

Assertion (A): Frequency is a measurable quantity. It depends on the source producing the sound.

Reason (R): Pitch depends on the sensation as perceived by a listener.

Sumit, a teenager, enjoys playing his music loudly. However, his grandmother consistently lowers the volume of the music player. Analyse the wave to identify which characteristic of the wave has been altered when the grandmother reduces the volume.

The picture shows three cylinders filled with water to a different extent. The tuning forks L, M and N in vibration produce louder sound when held above the mouth of the cylinders. Which combination is correct for hearing a louder sound of the tuning fork? 

The diagram shows the magnificent dome at Gol Ghumbaz at Bijapur. A boy standing at A whispers, and it is clearly heard at B across the huge dome. [Speed of sound is 330 ms⁻¹]

Assertion (A): The distance travelled by sound waves (x + y) should be < 33 m.

Reason (R): Sound reflected within 0.1 s is not heard by humans.

Which of the following statement is CORRECT?

The frequency of a stretched string is:

What is the ratio of wavelengths between P, Q and R?

John is trying to create musical notes using water-filled bottles, as shown in the picture. Which of the bottles is likely to produce a musical note with the highest pitch? Give reasons. 

When Shyam, the band leader, struck both the bass drum and the kettle drum with equal force, the bass drum emitted a sound measuring 120 dB, whereas the kettle drum produced a sound of 90 dB. Explain this discrepancy in the loudness.

Seismic waves have different frequencies. During earthquakes, why are short-length buildings more prone to damage caused by high-frequency seismic waves?

Ashish, Sameer, Aditya and Mohit were sitting on the terrace of Ashish's house listening to the songs playing on Aditya's mobile phone. Mohit, sitting in one corner, a little distance away from the others, requests to increase the volume of the songs. But Aditya says the volume is full. Sameer, being a smart guy, gets up, goes into the kitchen, brings an empty steel glass, places the mobile phone inside it and solves the problem. What is the reason for Sameer to keep the mobile phone in the glass?

Study the diagram and answer the following:

1. Arrange the following pendulums according to their natural frequencies (use < > =).
2. If Pendulum Z is initiated into oscillation, which pendulum among the others will exhibit the highest amplitude of vibration?
3. Give reasons for your answer.